Robotic systems implement devices—such as sensors and end effectors—to learn about and manipulate their environment. Some robotic systems include a coupling that serves as a mechanical joint. The coupling can provide electrical and mechanical connection between the device and the rest of the robotic system. In some cases, the coupling is configured to allow the device to rotate continuously, or at least through more than a full revolution, relative to the rest of the system. Various means of transmitting signals and/or power across such couplings have included slip rings (which feature a sliding or rolling electrical contact) and winding/unwinding coiled conductors that provide a limited range of rotation, for example.